1. Field of the Invention
The present invention relates to a light emitting diode (LED) driving device, more particularly, in which various circuits required for driving LEDs such as a direct current (DC)/direct current (DC) conversion circuit and a pulse width modulation (PWM) control circuit are integrated into one chip.
2. Description of the Related Art
In general, a cold cathode fluorescent lamp (CCFL) used as a light source of a conventional liquid crystal display (LCD) employs mercury gas, which may trigger environmental pollution. Besides, the CCFL is slow in response rate, low in color reproducibility and inappropriate for a smaller-sized and lighter-weight liquid crystal display (LCD) panel.
In contrast, a light emitting diode (LED) is environment-friendly, high in response rate with several nano seconds, thus effective for a video signal stream and capable of being impulsively driven. Moreover, the LED can reproduce color by 100% and alter brightness and color temperature by adjusting light amount of red, green and blue LEDs. Also, the LED carries advantages suitable for the smaller-sized and lighter-weight LCD panel. Therefore, of late, the LED has been actively employed as a backlight source of the LCD panel.
As described above, in a case where an LED array having a plurality of LEDs connected to one another is utilized in the liquid crystal display (LCD) backlight employing the LED, a driving circuit for driving the LED array requires a direct current-direct current (DC-DC) converter converting an input voltage inputted from the outside into a voltage suitable for driving the LED array, and a driving circuit supplying a predetermined constant current to the LED array. Moreover, the LED array driving circuit additionally requires a dimming circuit which enables a user to adjust brightness and color temperature arbitrarily or adjust brightness of the LEDs for e.g., temperature compensation.
Conventionally, various circuits for driving the LEDs are individually implemented using lumped devices such as a resistor or a capacitor or partially integrated into a chip, as demonstrated by e.g., a direct current (DC)-direct current (DC) converter.
Therefore, these conventional driving circuits for driving the LED arrays necessitate a board of a wide area for disposing the individual LEDs thereon. The conventional circuits also necessarily require a process for disposing the devices on an individual basis. Particularly, when dimming control is in need to control brightness of the LEDs by an external control signal, the board of a broader area and the devices are required.
Therefore, the conventional LED driving circuits involve higher costs due to a greater number of external devices, higher defect ratio during assembling, and less compactness.